1) Field of the Disclosure
The disclosure relates to polymeric coatings which enhance corrosion protection of substrate surfaces. The disclosure also relates to compositions and methods of making polyureide compounds that provide a durable, long-lasting, anti-corrosion coating when applied to substrate surfaces.
2) Description of Related Art
The structural bonding of metal to metal and/or composite type assemblies widely used in aircraft, spacecraft, rotorcraft, trucks, automobiles, boats, ships, bridges, power lines, and various other structures typically require a resultant structure which is reasonably resistant to the extremes of atmospheric conditions found in use. Bonded metal to metal and composite type assemblies must preferably be able to withstand the environmental conditions to be encountered. Of particular importance is resistance to corrosion of such structures. Corrosion of metallic and/or composite substrate surfaces on aircraft, spacecraft, rotorcraft, trucks, automobiles, boats, ships, bridges, power lines, and various other structures having metallic or composite surfaces, can result in increased maintenance to the structure and increased costs to repair and/or replace corroded structures. In addition, even a small amount of corrosion upon the surface of aircraft wings can significantly increase drag and dramatically reduce lift. Thus, corrosion resistance of substrate structures is extremely critical. With regard to metals, corrosion is the spontaneous destructive oxidation of metals. It is a natural process that attempts to reduce the binding energy in metals with the end result being that a corroded metal is oxidized, i.e., electrons leave the bulk metal and it changes its chemical properties. In some instances, the oxidized form of the metal is inherently corrosion-resistant but only to further oxidation. It is not corrosion-resistant to corrosive conditions, such as acidic species or galvanic corrosion. There are many kinds of corrosion which can attack metals, and it would be desirable to have a universal treatment process that can encompass and minimize corrosion on numerous types of metals rather than having multiple processes for each different metal. For aircraft, spacecraft, rotorcraft, trucks, automobiles, boats, ships, bridges, power lines, and various other structures having metallic surfaces, it is desirable to have a corrosion-resistant coating that is impervious to water and that minimizes the transfer of dissolved ionic species to the substrate.
Known methods and compositions exist for enhancing corrosion protection of substrate surfaces. Such known methods and compositions include the use of protective coatings and/or the use of sacrificial species. For sacrificial protection, the use of hexavalent and/or trivalent chromium ions is typically employed. For example, when a metal, such as aluminum, is processed for use in various applications, it may be anodized (treated to form a protective oxide) and simultaneously treated with a hexavalent chromium solution, such as strontium chromate, which deposits onto the aluminum and is sacrificially removed during exposure to corrosion-inducing salts or acids. A further protecting process is to paint the aluminum. The use of hexavalent and/or trivalent chromium in such known methods and compositions can involve additional time and expense.
Additional known methods and compositions used to mitigate corrosion formation on substrate surfaces include the use of adhesives bonded to the substrate surfaces. However, the use of such adhesives may require increased maintenance if the adhesives loosen at the interface between the polymeric adhesive and the substrate surface. In addition, zinc salts and alloys and titanium salts and alloys have been used but they either do not have a long life or require specific materials of construction to be used and are therefore not applicable to many substrates, such as aluminum, copper, composites, and others.
In addition, known methods and compositions using polyureide compounds in coatings applied to substrate surfaces exist. For example, U.S. Pat. No. 4,154,724 discloses polyether polyureides useful in the manufacture of plastics, sealants, molds, foams, and coatings. However, no corrosion protection of substrate surfaces is disclosed. In addition, U.S. Pat. No. 6,797,795 discloses the use of polysiloxane (amide-ureide) compositions and methods to inhibit formation of ice on the surface of a substrate. However, no corrosion protection of substrate surfaces is disclosed.
Accordingly, there is a need for a composition and method for corrosion protection of a substrate surface that provides advantages over known compositions and methods for corrosion protection of a substrate surface.